Rotary atomizers - A possible alternative to pressure nozzles

Rotary atomizers can be a possible alternative to pressure nozzles or pneumatic atomizers. Especially when spraying with conventional nozzles is problematic or does not work.

If, for example, suspensions are to be atomized with pressure nozzles, this quickly leads to blockages. Especially when low volume flows are atomized and the nozzle orifices are correspondingly small. If the liquid has a high viscosity, the nozzle may also fail quickly.

Twin fluid nozzles cannot be used for every application. If no additional gases (compressed air) may be introduced into a process, their use is ruled out. It should also be taken into account that the spray pulse of these nozzles is high. In combination with fine droplets in the spray, overspray problems can quickly occur.

In these cases, and of course for other applications, the rotary atomizer can be an interesting alternative. This is because it offers a number of advantages with which even difficult tasks in atomisation technology can be solved.

How do rotary atomizers work?

Rotary atomizers belong to the so-called mechanical atomizers. This means that neither a high-pressure liquid nor a pressurised gas is required for atomisation. Instead, the energy required for the atomization process is transferred directly from a rotating atomizer body to the liquid.

The advantage is obvious! The energy required for atomizing the liquid is directly supplied mechanically and energetically in a particularly favourable way. The complex and costly production of compressed gas, for example compressed air, is no longer necessary. It is sufficient to feed the liquid or suspension to be atomized to the rotary atomizer under low pressure. Even a low hydrostatic pressure is often adequate.

The simplest rotary atomizer in terms of design is the flat and rotating disc. Picture:  IBR Zerstäubungstechnik GmbH
  1. The liquid to be atomized emerges from the feeding nozzle at low speed and minimum pressure difference.
  2. The flat disc rotates at the angular speed ω
  3. Due to the centrifugal acceleration, a liquid film forms. This becomes thinner with increasing distance z from the center.
  4. Droplets are created, whereby the drop size itself as well as the drop size distribution can be controlled in certain areas.

The flat and rotating disc is therefore the simplest design of a rotary atomizer. The advantage is that the liquid or suspension to be atomized is supplied at low speed. Thus, large free cross-sections can be used for the feeding inflow. Since there are no other installations, such rotary atomizers are considered to be blockage-free.

Another important advantage is that the rotary atomizer is self-cleaning when operating with most liquids!

What has to be considered when operating the rotary atomizer?

These atomizers are very flexible in operation. This means that they can be adapted to the requirements with regard to the volume flows to be atomised as well as with changing rheological properties. However, a number of aspects must be taken into account.

To design a rotary atomizer, the areas of the rheology and the desired volume flow ranges must be known! Without this data, a rotary atomizer cannot be reliably calculated!

These atomizers naturally provide a linear spray pattern all around. Naturally, the drops follow the acceleration of gravity or superimposed gas flows. It must be checked in advance whether this spray pattern is acceptable for the specific process or production engineering process.

If high volume flows have to be atomized into fine droplets, the required diameter of a rotary atomizer can become large. It should be noted that the mechanical load will then also be high, depending on the speed. The use of several atomizers may be considered.

Depending on the operating conditions, different droplet formation mechanisms occur. The so-called dripping is usually undesirable. The filament formation and occasionally the lamella decay, however, represent desired drop formations. This must be taken into account in the design.

It goes without saying that we take these important aspects into account from the very first consultation. If, for example, important rheological properties are not known, we will gladly determine them for you as a service!

Rotary atomizers offer a number of advantages!

One of the biggest advantages of this atomizer is that almost all constructive forms are considered to be almost blockage-free. In addition, they can usually be operated in any position. The reason for this is that the centrifugal acceleration is usually significantly greater than the acceleration due to gravity.

The cup atomizer is a special type of rotary atomizer.

If small volume flows of liquids are to be atomized into fine droplets, the cup atomizer is particularly suitable. This is a special type of rotary atomizer. The liquid can be fed either from above through a supply line or alternatively through a hollow shaft in the drive.

As with all rotary atomizers, almost monodisperse droplets can also be produced with a cup atomizer over a wide operating range. This means the drops all have an almost identical droplet diameter. The monodisperse droplet size can even be adjusted in certain areas in the area of the so-called thread disintegration.

It is also very interesting that these atomizers can deliver particularly fine droplets of almost the same size in the area of thread disintegration with highly viscous liquids! This is also possible with small volume flows of liquid to be atomized. Classical nozzles such as pressure nozzles and pneumatic atomizers, on the other hand, always provide a droplet size distribution.

For certain applications, cone atomizers are used in addition to the cup atomizer.

For certain applications, cone atomizers are used in addition to the cup atomizer. With this type of construction, suspensions can usually also be atomized without any problems.

Of course, a drive and power supply from the underside is also possible here. The design depends on the respective requirements.

The rotary atomizer is particularly well suited for interior coatings!

If tubes or other hollow components have to be coated from the inside, the use of rotary atomizers is of course particularly advantageous for the following reason:

As already mentioned, these atomizers deliver a linear spray with an angle of 360o. This property can be used to achieve a uniform internal coating. For this purpose, either the component to be coated or the atomizer is moved in the longitudinal direction.

In medical technology, small tubes often have to be coated from the inside.

In medical technology, for example, thin tubes often need to be coated from the inside. Conventional atomizers often cause problems here. On the one hand, the areas to be coated cannot be precisely defined with these. On the other hand, the overspray problem plays a major role.

Since usually only a small volume flow per cycle has to be atomized, rotary atomizers are correspondingly small. They can therefore also be inserted into very thin tubes!

Of course, this principle can also be implemented for pipes with larger diameters and lengths!

IBR Zerstäubungstechnik GmbH has already successfully designed rotary atomizers with which even contoured pipes of considerable length can be coated evenly from the inside. The layer thickness can be precisely adjusted by means of the controllably supplied volume flow in conjunction with the specified traversing speed.

Comprehensive advice on rotary atomizers and applications.

We not only provide comprehensive advice on the use of rotary atomizers.

Moreover, we have our own software to calculate the permissible operating ranges. If almost monodisperse drops with a given droplet diameter are required, we can determine the required diameter and the speed of the atomizer. If the rheological data of the liquid to be atomized are known.

Of course, we can also determine droplet trajectories for you on request. Even with superimposed gas flows. For this we use our nozzle test benches or alternatively numerical fluid mechanics; CFD.

In addition, we would of course be happy to help you with calculations of mass and heat transfer!

Discuss the possibilities of using a rotary atomizer with our experts!

Get comprehensive and non-binding advice now on the prospects of solving your problems with rotary atomizers! Our experts are personally available during our office hours on the hotline

+49 251 2 87 99 53 – 0

at your disposal. Or alternatively use our inquiry form.